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Tuesday, 24 January 2012

Sensitometry and the Plotter/Matcher, Part II

You probably remember Part I, from a week ago Saturday. You might want to go back and re-read that before diving into this part. First, to reiterate: no B&W film photographer needs to practice sensitometry. It's absolutely not necessary for doing good work. This article does, however, contain information of real value for all APUG-type B&W photographers, so don't skip it if you're one of those—even if you have no intention whatsoever of buying a densitometer or practicing sensitometry.

As an aside, since a week ago Saturday I have acquired not one but two densitometers...

The second is a very nifty secondhand Heiland TRD2 which is a transmission and reflectance densitometer in one, meaning it reads both negatives and prints. It was offered to me by TOP reader Jeff S. for a good price after I had already "won," on eBay, a very nice Eseco Speedmaster TRC-60D, after various web researches turned up a number of recommendations for it from photographers doing what I wanted to do. I was amazed when I got the Heiland—for someone who has only used big, heavy Macbeths in various workplaces, the box seemed too small and altogether too light to contain a densitometer. The Heiland turns out to be a wee little thing.

Eseco is still very much in business in Oklahoma, and still includes densitometers in its product offerings even though there's very little call for them—the current model is the battery-powered SM-10T. When I asked if the TRC-60 could still be serviced, the answer was "almost"(!). Last made in 1985, the parts for it are now mostly gone, but the Service Manager told me that Eseco still has people around who know it well enough to get most any broken one working again. On the good side, he said working ones will most likely keep on working, with no need for service. (Densitometers are apparently very robust devices, that typically keep on going just fine for years and years.)

The all-important FDPSo here are a few reasons you might need a densitometer, in descending order of importance: If you review B&W films and papers for a living; if you use lots of different materials and you like to get up to speed quickly and efficiently; if you're looking for an optimal FDP combination (more on what that means below); or if you just think that sort of thing is fun. (Maybe that last reason should go first.) Another reason is if it helps you to work at the limits of control, although—I'll say it yet again—you don't need sensitometry to do high-quality work in B&W.

One thing it does help with, indisputably, is understanding FDP combinations, and this is where Phil Davis (author of Beyond the Zone System —which, as one Amazon reviewer points out, could have been called "Sensitometry for Photographers") comes into this picture. There are three things that determine the look, or the tonal signature, of traditional B&W materials—the film (F), the film developer (D), and the paper (P)—"FDP." This is important: there are lots of people (one might even say "all people" within loose tolerances) who "test" B&W materials using what I'd call the "fake experimental method." That is, they tightly control all of the variables and change only one, then draw their conclusions from the differences they observe, assigning those differences to that one cause. The problem is that all three variables influence the final result.

That is, if you use film A, developer B, and Paper C, you can't just switch out developer B for developer D and reach any meaningful conclusions about either one—because you're only testing them with film A and paper C, and your conclusions are only valid for those variables. This doesn't stop people from generalizing madly based on their supposedly "rigorous" trials. Phil was quite contemptuous of this—if you changed one of the three variables and drew conclusion x from it, he could suggest changes to the other two variables that might change your conclusion to y and not x. Add to this the variations within each variable—how much development a film received, different developer dilutions, which paper grade you use—and you have a tarpit that no one gets out of alive.

Phil's belief was that measurement was the only thing that could save us from the tarpit. He once said to me that with his measurements he could learn in an afternoon as much as an "eyeballer" could learn in the darkroom in a year. (Eyeballer was his grudgingly affectionate term of disapprobation for reprobates like me who flew without instruments.)

Phil's Plotter programI just had a great conversation with my old friend Fred Newman of the View Camera Store, who must be close to the friendliest guy on god's green earth—or should I say, god's arid, sun-drenched, sand-colored earth, since he's down in Scottsdale, Arizona. The current version of the old Plotter/Matcher program, now called Plotter for Windows, which was ported to Windows by David Jade and has been improved since Phil's death by Fred and David, will run on Macs under an emulator, so he's going to send me a copy—and I'll review it, if I can, in due course. So I'm going to make this rather brief, to just give you a general idea of it.

To show you how it works, more or less, I first pulled out of mothballs my old Macintosh Powerbook 180, which is the only computer I have that Phil's old Plotter/Matcher will run on. (This computer sure was a lot more handsome when it was new!) The old machine is balky, and the trackball needs a good cleaning, so I was barely able to make it work.

To begin with, here's a typical "family" of film curves—this is Ilford 400 Delta sheet film, developed in straight ID-11 (Ilford's version of Kodak D-76). The test films were developed in BTZS Tubes for four, five and a half, eight, 11, and 16 minutes. You can see how the high values get more dense with more development (that's log density on the y axis) and how the contrast goes up—that's shown by the basic slope of the curve. You can also see that the speed point (.01 above fb+f, or the point where exposure begins to register) moves to the left slightly with increased development—yep, film actually gets "faster" (slightly) with more development.

So that's F (film) and D (developer). Different developers might change any of this data even for the same film: the speed point, the contrast with any given development time, even, in some cases, the shape of the curve.

(I can't resist an aside to those who are participating in what appears to be a fad on flickr for extremely dilute Rodinal: Rodinal in high dilutions frequently develops to completion/exhaustion, meaning, the curve stops changing after a certain amount of development time has been reached—so it's possible that you're developing for an hour and not making any difference at all over developing for, say, fifteen minutes*. You'd have to test to be sure. Suffice to say that there's a pretty high likihood that with extremely long developing times in extremely dilute Rodinal, not only is no magic happening, but nothing may be happening at all. On the good side—sort of—that's also why "stand development" with Rodinal doesn't result in streaky, blotchy negs—because if nothing's happening, nothing bad can happen.)

Now here's a family of paper curves. This is Agfa Multicontrast Classic, one of my favorite papers, which has recently been revived (on a whiter base) under the name Adox Premium MCC**. To begin with, remember that this is paper, which is the inverse of the negative—so this curve is "upside down"—the less dense highlights are now at the bottom and the denser dark areas at the top.

And here's where most any B&W printer can learn a few things. Do you see how weird and lumpy the lowest-contrast curve (labeled "2") is? That's the reason you should never target your negatives to a low contrast grade on VC papers—shoot for at least grade 2 or even 2.5 or 3 to get into the middle of the paper's comfort zone. Also, ignoring the outliers—1 (all the way to the left) and 7 and 8—do you notice something else funny about the remaining curves? Note how the curves don't really begin to diverge from each other until about 1.0 density. That's when the different grades start to split apart. What that tells you is that with this paper, highlight contrast doesn't really change much with changes in filtration—and that turns out to be true for most VC papers. That tells you two things—first, you need to match your film to a paper based on the way you want your higher values to look, and second, when you expose under the enlarger, you do just the opposite of what you do with film—expose for the highlights and then adjust contrast with contrast filters. So when you make a test strip with VC paper, evaluate the highlights, disregard the shadows.

But to continue. Here's the payoff, and what the "matcher" part of Phil's Plotter program does. There are a couple of intermediate steps (mainly, you have to pick one particular film curve and one particular paper grade), but the Plotter basically matches the film's curve (in, you'll recall, the developer you chose) to the paper's curve, and gives you the charactersitics of the FDP***. Phil also devised a way to give users a quick visual read on what's going on—the two bar charts on the right-hand side.

This chart happens to represent my own standard materials at the time—35mm Tri-X 400 in D-76 1+1 for 8.5 minutes, plotted against Agfa MCC in Neutol WA 1+7. The bars show the tones from both ends expanding into the middle—the dark zones raised in value considerably, and the highlight tones taking up a bit more of the scale. And that is indeed how they printed—giving just the look I happen to most like.

A year's work in a dayTraditional B&W photographers who printed their own work spent a great deal of time and effort struggling to correct for the inherent characteristics of their materials—"fighting" the materials, as Phil used to say. Much of the darkroom heroics you read about all over the literature were simply the result of the photographer wanting a different look than the materials, combined, wanted to yield. Contrary to (very) popular belief, "trying lots of different materials for yourself" was really no better than stumbling around in the dark to see what you might bump into. When you got the FDP combination that matched the look you wanted, as often as not the negative would "fall on to the paper," as printers sometimes put it. Printing became easy. Well, easier, let's say. Darkroom workers had nothing but experience and long familiarity with their favorite materials to guide them, and that was indeed serviceable knowledge. But even then they were basically lost when it came to replacing old materials they liked with a new substitute, when, for instance, an old film or developer or paper was discontinued—and that's been happening regularly since optical/chemical photography was young, not just recently.

Phil Davis's idea was to spare people all that, and just let them find quickly the materials that suited their tastes. Once you knew how you wanted that bar chart to look—approximately where you wanted those "reference grays" to go on the "print grays" bar—finding different materials that yielded the look you liked was just a matter of poking around in the data until you found what you wanted. If you changed one variable, you could see exactly what effect it had on the tones—and, if you wanted to, you could change something different to change it back again. Each change of variable represented how much time in the darkroom—a hundred prints? At least a dozen. Phil was really right—as long as you had a large enough database of materials tested, you could gain the knowledge of a year's work in a day.

• • •

And in closing, may I just say how much I miss Phil, who died in 2007. (There's a picture of Phil and me here.) For more than six years we exchanged emails, often long ones, daily, sometimes more than one. We were not in contact much in the year or year and a half before his death—he was unsentimental about his own demise, and found my solicitous concern for his health after he got cancer tiresome—but for many years he was a good friend and faithful correspondent, as well as a wise and always challenging teacher. On the phone today, Fred mentioned that Phil had forgotten more about B&W technique than most photographers ever know. Truer words were seldom spoken.

Mike

*Don't think I'm so smart—I learned this lesson the hard way. When I first tried extended development in dilute Rodinal—1:100 or 1:150 for 45 minutes or an hour, I think it was—I mentioned in an email to Phil that I'd gotten very pretty negatives but that I'd nearly driven myself out of my gourd with boredom. "Anyway, it works," I concluded. About half a day later Phil emailed me back and told me to try the exact same technique, but for 18 minutes or whatever it was. I did, and the negatives were...to my amazement, essentially identical with the first ones. He had run some quick tests in the intervening time and determined what I conveyed to you above.

**Agfa Neutol WA, which was my choice for the best paper developer for Agfa MCC, has also been revived, under the name Compard Print WA.

***Some readers will have realized by now that when you scan negatives, you're not quite seeing the way that film and that developer were intended to look, because the manufacturer designed the material to be matched subsequently to a printing paper. When scanning, you don't get the paper curve's influence on the result. You can also apply other curves at will in Photoshop or any other image editor that has a curves function.

Comments

A long time ago, I wanted to buy a basic transmission densitometer. The X-Rite 331 was my choice. It has been 100% reliable over the years and extremely accurate when occasionally compared to very expensive, frequently calibrated lab units.

If in the market again today, I would not hesitate to purchase X-Rite's current version, the 341C:

It appears to have changed only by using flat panel switches instead of mechanical ones on top and employing nickel-metal-hydride batteries rather than nickel-cadmium. I've had no issues with either of those things, but think the improvements are worthwhile nonetheless.

Ahhh...sensitometry & the old Macbeth TD-502...I remember them well. Running the Ohio University Film Production Laboratory, I built a simple Sensitometer, which combined my favorite things--machine shop work & electronics--to provide calibrated exposure
strips. Then we'd monitor our processing results with the Macbeth, for which I'd built a separate, calibrated power supply, allowing us to "dial in" the printer lights on the expanded scale voltmeter, as needed. One of the best real jobs I ever had!

A couple of propellerhead comments: surely there is someone out there who could do a port to the new mac environment in their sleep assuming the original source code is available and there was interest ( but that someone ain't me ). Alternatively, looks like the job could be handled in Excel, no programming required.

Very dilute developer behaves a bit like water-bath development where you take the film (sheet, most often) from developer to water bath and back. In both cases, the deal is that it holds back development in the highlights due to exhaustion of the developer there, while giving the developer LOTS of time to work on the shadows.

So, basically, this is a primitive form of HDR; you're taking a brightness range exceeding that of the film, and compressing it down.

Ansel Adams used water-bath development on the negative for the famous moon rise over Hernandez, and still just barely managed a printable neg.

David,
As with many things in B&W photography, that's a nice theory, but it doesn't really work--it hardly changes the shape of the curve at all, and the differences are below the threshold of noticeability to the eye. To test it you need to develop one neg that way and one with a more standard dilution to the same density range, then plot their curves against each other.

There are lots of things in B&W that are popular because they sound plausible. A number of them are in effect harmless placebos--they don't hurt, but they don't help, and if they make people feel better, well....

Water bath development doesn't work any more either. It worked with the old thick-emulsion films, but those are long gone. The thin-emulsion films of today don't hold any developer to speak of so the water bath idea doesn't (wait for it) hold water. (Sorry.) But by all means try it for yourself.

Again, as the article says, it's best not to fight the materials. Just pick an FDP combination that raises the shadow detail, or that allows you to place the shadow detail higher on the curve, and there you are--no further special measures needed (unless they make you feel better).

Mike,
As long as we are talking about stand developing, water baths, and things that sound plausible, but aren't factual:
Is it in fact the case that n-1 exposure AND development is workable for B&W negatives that are only for scanning?

Sensitometry also reveals that Ilford contrast filters for enlargers are mislabled in sequence. While I haven't checked their filters for a few years, all samples that I checked until then showed the problem. The filter samples spanned many years of production.

I pity the poor darkroom worker who assumed that the Ilford #4 filter produced more contrast that the #3-1/2 filter. In reality the #4 just about matched the #2-1/2, and there were some other errors in the sequence.

[Mike replies: Not true, and the experiment at the link is fatally flawed, at least for showing what it purports to show: cold light heads don't work as intended with variable-contrast paper because they emit too much blue and too little green light--blue and green being the two colors of light that the emulsions in VC papers are sensitive to, and that the yellow and magenta filters are meant to modulate. Not only that, but the spectral output of cold light heads changes with temperature. If I recall correctly, there was attempt made to market a cold light head that would work with VC papers, but it didn't yield as consistent results as enlargers with ordinary dichroic-style heads.

The linked chart is however the most precise illustration I think I've seen of what goes wrong with VC filters and cold light heads! —MJ]

As I read this post, I had moments of nostalgia for my old darkroom, with its D2 Omega, film tanks, paper trays, etc., etc. But not many. Somehow, I really don't miss the wet darkroom. True, the learning curve on PS5, and the like can be long, but I sure seem to get better results, and in color too, as well as B&W. Nope, even though I still shoot some film, I'll scan it and print digital. Digital isn't perfect, but what is??

I did the Rodinal diluting and stand development thing partly due to time constraints. I could start the development process put the kids to bed and then finish the development thus saving myself a few minutes and not being precise meant it could be 45 or 90 mins and still get the results i wanted.

Mike, I had to laugh about your phrase "APUG-type B&W photographers". I guess since I own a Heiland densitometer and understand all this BTZS stuff, AND visit APUG that I fall into this category.

But what exactly does that say about me? I have always been suspicious when I have been slotted into some readily identifiable category, and it makes me wonder if I need to adopt some counter-typical signifier such as a funny hat, or a second hobby of, oh, I don't know - maybe ham radio operator specializing in arranging helicopter rescues of stranded livestock to ensure I am not pigeonholed.

Only got a X-rite 8xx type (and which local Hong Kong X-rite dealer still selling parts which I got just in case). Also got a set of all these. Due to some family issue, I have to wait but this view seems align with my experience.

The only one particular thing I learn from his book is to use incidence meter to do this. A bit odd and would try later.

A few notes from my perspective, for film testing. The most difficult thing for me to get my head aroud was setting the personal speed point. If you are familiar with BTZS you know what I'm talking about. Long story short, besides a desitometer, acquirig a sesitometer is a god send for testing.

With the help of a couple of kowledgable friends, I discovered the EG&G MK VI &VII are the preffered units. Hard to find, but if one is serious about film testig these gizmos will simplify the tasks. Look on ebay for used models.

I have the Eseco Speedmaster, sourced directly from the factory as factory refurrbed unit (this was after receiving 2 DOA from ebay sellers). The price was very reasonable.

I also have a Xrite 810 which allows direct capture from a serial port input but now most computers no longer support RS232 connections.

The Matcher program really works though groking the software was a bit difficult for me at first.

I do wish 31 step-step tablets were supported. And getting the data package that Phil and Fred created is also very worth while and istructional.

BTZS IS very gear intensive and may not suit everyones demeanor for gizmo-stuff or computer phobes. My best advice if one wishes to stick their toe in the BTZS pool is to contact Fred or Dennis at the View Camera store.

A friend of mine uses highly-dilute stand developing for just the reason that you mention. He can get his negatives soaking and never has to worry if the baby starts crying or someone rings the door-bell. 45 mins... 55 mins... he still gets pretty consistent results. He's a multi-tasker.

For me, I just can't help but stare at that little tin can, waiting for the sound of the buzzer.

As an FYI, the former online magazine,Magna-Chrome (not to be confused with this company http://www.magnachrome.com/), published an article several years ago explaining BTZS and offered a freely distributibed PDF and Excel spreadsheet.

MC is now defunct but I have copies of the PDF file and spreadsheet utility. If you would like a copy of each, e-mail me and I'll e-mail you a YouSendIt link so you can download them.

Yeah, but there are a few other variables as well. The enlargers optical system makes a pretty huge difference. What is a unprintable highlight in a collimated point source enlarger due to the callier effect is just fine in a cold light enlarger. I believe the shape of the response curve changes as well.

I once had the experience of working in a darkroom with an old safelight that was just an incandescent bulb painted red . We upgraded to a Thomas Duplex and all the highlights in the prints became chalky. It turned out that the old safelight had been fogging the paper just enough to add some density to the highlights without reaching the threshold of noticeably fogging the borders of the print. The guy who shot halftones of them had a memorable WTF moment when all our prints went weird on him.

Right out of school I worked very briefly for a guy that insisted that enlargers needed to be "broken in". One enlarger would "print by itself" and the new enlarger would require much fussing about, hand waving, and burning in. After a while the new enlarger and lens would be "broken in and printing by itself". Of course he was chain smoking the whole time and his FDP was calibrated for a lens and condenser coated with a film of cigarette smoke. Apparently one of his previous workers employment was terminated when "he broke the old enlarger" by "doing something weird to the condensers or the lens or something when he cleaned it" hence the new enlarger that needed to be broken in.

Rule of assisting: Don't clean any gear until you have seen if and how the photographer does it. Don't offer to fix the bent reflectors , busted softboxes, and obviously too long power cables .
And don't dare even think about that busted up umbrella that looks like the dog peed on it or it was used to serve fried chicken out of and I can't believe he's shooting the main light through it and does he know that there is a hole in the compendium where the gel fits?

Oh, and developing to completion rocks, modern thin emulsion films not so much. I fondly remember a college photo class where one assignment involved developing Pan-X for 12 hours. In retrospect I think it may of had as much to do with all the photo students going to classes whacking those little Nikor tanks every five minutes. In the art history slide lectures. Whack! Photo student here!
Does diafine still work on modern films?

Mike, of course you don't but if you scan using SilverFast (as my expirience goes) you do get to the point where you can adjust the scan for the film being used. My credo is simple, I always use the film developer of the company that made the film. I use Ilford Pan F Plus and Delta for B&W and use DD-X as a developer and develop using the standards given by Ilford. If my exposure was correct I should get the result that Ilford imagined (more or less) and thus when I scan using the Ilford Delta and Pan F Plus profiles in SilverFast I should wind up with evenly matched negatives, no matter what (and I'm pleased to say, I do).

But I was wondering, SilverFast has a little densitometer build in.....Have you (or any of the readers) checked that and is it any good.....e.g. could I use a scanner as a densitometer?

"But even then they were basically lost when it came to replacing old materials they liked with a new substitute, when, for instance, an old film or developer or paper was discontinued," as for example in the case of the Ilford Delta 400 sheet film cited above. Today it's only available in 35mm and 120.

Many thanks, Mike: this throws a very revealing light on some vividly recalled darkroom frustrations. In your third screen shot the bar graphs on the right give an immediately comprehensible explanation of what's happening. It's a bit like the ZoneMapper control in Lightzone, perhaps.

Mike- the reason for stand development times of an hour to an hour and a half is to let you go and watch a film or the TV, whilst you reflect on whether the shot you just took really is good enough for the Pulitzer. 18 minutes just doesn't cut it.

"That tells you two things—first, you need to match your film to a paper based on the way you want your higher values to look, and second, when you expose under the enlarger, you do just the opposite of what you do with film—expose for the highlights and then adjust contrast with contrast filters."

I have the feeling that this is important advice for a darkroom novice like me. I'm just not sure how to follow it. Any posts about darkroom printing will be much appreciated.
Paul

Adding to what Mike said, cold light heads typically have narrow, spiky spectra, so their peak emissions may not at all match the peak absorptions of the dyes in the variable contrast filters. Furthermore, VC papers have spiky spectral sensitivity (see my section on VC papers in POST EXPOSURE) and expect to be dealing with a "white light" source, so who knows what the paper is actually seeing.

The fact that you got extremely different results for each different combination of paper and filter set you used should have been a big clue that something wasn't right.

One factor that DOES matter is the age of the filters and how much they've been used. In particular, the magenta dye used in some VC filters is relatively fugitive, so it's possible to have Grades 4 and up light-fade enough that they actually become lower in contrast than Grade 3. That big a change is readily seen with the naked eye-- when your Grade 4.5 filter looks merely rosy pink, it's kind of a big hint-- but lesser degrees of fading may not be at all visually obvious.

Careful workers keep some kind of quick and dirty reference neg & print on hand and every couple of months bang out a few quick prints just to make sure their filters are still in A-1 shape.

Re link from William Schneider showing apparently "mis-labelled" Ilford filters: chart states that an Aristo V54 lamp was used, reportedly this lamp does give close to proper grade spacing with VC papers without the lack of low contrast and "bunching" at the end a regular cold light lamp will give (I've only personally used the regular lamp with filters though so I can't confirm from direct experience that the V54 lamp is really any better. This link to something originally in Photo Techniques mag appears to show the V54 does work though: http://www.light-sources.com/sites/default/files/v54_lamp_color.pdf). William Schneider's link definitely would make me wonder about the filter set he tested.

If you calibrate your scanner with a standard transmission step wedge, it should be usable as a densitometer -- especially if it's CCD-based, as CCDs are among the most linear of all measurement devices.

The problem is when you're at high densities and thus near the scanner's noise floor (since high density = low transmission). On negative film you'll get the densities for the shadows right, but the numbers obtained for highlights are unlikely to be useful, unless your film is developed to give very thin negatives.

The V54 lamp is an improvement over the older bluish lamps. I am able to get very even grade spacing using it, as measured using a reflection densitometer reading step wedges. Here's another chart showing that the V54 (with Kodak PolyMax filters) achieves a true -1 grade even in Dektol, but especially with Ansco 120 developer...

I do want to mention one more thing. In the March/April 2007 issue of Photo Techniques magazine, Kodak scientists Dick Dickerson and Sylvia Zawadzki also mention that they discovered some mislabled filters in a story titled "Variable-Contrast Filters - Are They All They Claim To Be".

They advise spreading out the filters to check for a smooth color progression. Both of my MG filter sets fail that test, and it shows in the sensitometry data. It's hard to argue with numbers.